The present invention relates to an open-end spinning rotor, comprising a rotor shaft, a rotor cup and a coupling device to releasably connect the rotor shaft and rotor cup, the coupling device having locking bodies, which are arranged in a holding element and lock the rotor cup and the rotor shaft in the axial direction as a consequence of the centrifugal force during operation of the open-end spinning rotor, and wherein a resilient element is associated with the locking bodies and the resilient element cooperates with the locking bodies in such a way that the locking bodies also lock the rotor cup to the rotor shaft in the axial direction at a standstill.
In the past, open-end rotor spinning machines used in the textile industry were usually designed in such a way that the spinning rotors were mounted with their rotor shaft in the bearing interstices of a so-called support disc bearing arrangement and were driven, in this case, by means of a tangential belt along the length of the machine.
These spinning rotors, in which the rotor shaft and the rotor cup are virtually non-releasably connected by means of a press fit, may, if necessary, for example in the case of wear or in order to manufacture a different type of yarn on the rotor spinning machine, be installed or disassembled from the front through the opened rotor housing.
Currently, electric motor-driven spinning rotors are increasingly gaining importance. A single motor-driven spinning rotor of this type is, for example, known from European Patent Document EP 0 972 868 A2. The disclosed spinning rotor is supported with its rotor shaft in a magnetic bearing arrangement.
The magnetic bearing arrangement consists here, of a front and a rear bearing point, these bearing points in turn each having axially opposing permanent magnet rings. One of these permanent magnet rings is fixed here, in each case, on the stator, while the other permanent magnetic ring revolves with the rotor shaft.
As the installation and disassembly of spinning rotors mounted in this manner requires a not inconsiderable assembly outlay, the rotor cup is in each case releasably connected to the rotor shaft in these spinning rotors. A possibility for a releasable connection of this type is described in European Patent Document EP 1 156 142 B1. This is realised by means of a coupling device, which consists of a magnetic bearing arrangement for the axial locking of the rotor shaft and rotor cup and a mechanical anti-rotation device, which prevents any relative rotational movement between the rotor shaft and rotor cup by means of positive engagement. A receiving sleeve is let into the rotor shaft by means of a press fit. A permanent magnet and an internal polygon are let in the receiving sleeve in the axial direction one behind the other. The rotor cup has a stub shaft with an external polygon, which corresponds with the internal polygon.
Types of connection, which transmit torques and powers from a rotating shaft or a rotating pin to a hub or vice versa from a rotating hub to a shaft or a pin, are called shaft-hub connections in mechanical engineering. The internal polygon, in conjunction with the external polygon, forms a positive shaft-hub connection. However, even before the establishing of single motor drives, there were attempts to form the connection of the rotor cup and rotor shaft releasably. Examples are found in German Patent Documents DE 38 15 182 A1 and in DE 196 18 027 A1.
German Patent Document DE 38 15 182 A1 discloses various examples, in which the coupling in the axial direction and the torque transmission from the rotor shaft to the rotor cup is realised either by a non-positive or a positive connection. To transmit the torque, in one embodiment, the rotor cup is provided on the external region of its base with connecting pins, which are introduced into two axially parallel bores of a coupling disc fastened to the rotor shaft. For axial fixing, inter alia, a spring steel strip bent in an undulating manner or an S-shaped resilient locking element are proposed. Both parts deform under the influence of centrifugal forces and then engage in indentations at the end of the connecting pins. In the rest state, the rotor cup and rotor shaft are not axially locked. Presumably for this reason, the connecting pins are relatively long to prevent the rotor cup from falling out in the rest state under the influence of gravitational force. The long connecting pins are rather unfavourable for handling.
The generic German Patent Document DE 196 18 027 A1 discloses a coupling mechanism between the rotor cup and rotor shaft, which produces an exclusively non-positive connection both in the axial direction and also for torque transmission. This is a centrifugal force coupling with spherical locking bodies. When the spinning rotor is made to rotate, the centrifugal forces, because of the construction of the coupling, ensure a locking in the axial direction and in the rotational direction. In addition, the coupling has a resilient element, which, for example, can be configured as a rubber block or as a spring element. The resilient element is arranged in such a way that the locking bodies can even be pressed outwardly without a rotational movement in relation to the rotational axis of the spinning rotor. A locking is thus also present when the spinning rotor is at a standstill. To connect the spinning cup and rotor shaft, the locking bodies can be easily pressed together. The disadvantage in this arrangement is that with an increasing rotational speed of the spinning rotor, the purely non-positive transmission of the torque no longer works reliably.
According to German Patent Document DE 196 18 027 A1, the coupling with the locking bodies is to be configured as a separate component. The manufacturing tolerances add up in accordance with the number of components, so that more components lead to greater imprecisions and therefore to a greater imbalance. At the high rotational speeds at which spinning rotors are operated, this imbalance can lead to problems, through to damage to the spinning unit.